/**
 *    Copyright (C) 2024-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the Server Side Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */
#pragma once

#pragma once

#include "mongo/db/pipeline/percentile_algo_accurate.h"
#include "mongo/util/modules.h"

#include <boost/optional/optional.hpp>

namespace mongo {

/**
 *'ContinuousPercentile' algorithm for computing accurate continuous percentiles
 */
class ContinuousPercentile : public AccuratePercentile {
public:
    ContinuousPercentile(ExpressionContext* expCtx);

    static double computeTrueRank(int n, double p) {
        return p * (n - 1);
    }

    static double linearInterpolate(
        double rank, int rank_ceil, int rank_floor, double value_ceil, double value_floor);

    boost::optional<double> computePercentile(double p) final;

    void reset() final;

private:
    // Only used if we spilled to disk.
    boost::optional<double> computeSpilledPercentile(double p) final;
    std::pair<boost::optional<double>, boost::optional<double>> _previousValues = {boost::none,
                                                                                   boost::none};
};

}  // namespace mongo
